There as a huge wave of mindful consumerism happening right now. It feels like within the last 2 years its gone from a niche market to mainstream. There are so many different categories it might be a little hard to fully understand what you are buying into. That is why I decided to put together a little guide explaining what is what and how they are different.

Ethical Fashion (may also be called Fair Fashion)

When a brand calls themselves ethical it means that the people producing the clothing are treated and paid a fair wage. Pretty simple right? 
This does not cover the materials used, the environmental impact or how they treat animals, it's really only about who is making the clothes.
I would be careful with brands claiming to be ethical though because this word can be used a lot in green washing. It's a great way to sound like you are doing things right but might be doing nothing at all. A good way to know if a company actually is practicing ethical production is through certifications such as Fair Trade. With smaller companies like mine, where the designer and their small team makes everything, they may not have the budget to pay for the fair trade certification, but you can easily ask them over email about who makes the clothes and use your judgement from there.

Slow Fashion

Slow fashion is another term that risks being used in green washing. This is because it really has to do with the brands philosophy; how many collections are being produced and the overall aesthetic. Slow fashion brands don't follow mass trends, since the goal is to make clothing that you will keep wearing. If a brand claims they are slow fashion but you see them rolling out new items each week and they have styles that you'll wear once or twice and get sick of... the chances are that is not at all slow fashion.
Slow Fashion is about making quality styles that you won't tire of, think about a capsule wardrobe philosophy. Typically they are also using eco materials and ethical practices, but they are not always tied together.

Sustainable Fashion

This one is all about environmentally friendly, renewable, organic materials. Look for Organic Cotton, Hemp, Tencel/Lyocelll, Organic Linen, Organic Wool, Recycled Polyester, Recycled Down, etc. As you can tell, this does not mean vegan. Sustainability refers to how the materials used and production practices affect environment. A great example for this is Tencel; Tencel/Lyocell starts off as sustainably grown Eucalyptus Trees that are then harvested and broken down into pulp and then fibres. It is a complication process, however, all the compounds (which must comply to non-toxicity standards) and water used is then reused and reused over and over. We call this a circular production process. As a result there is little to no waste to produce Tencel. 
The easiest way to spot green washing in this category is if a brand claims it is sustainable and uses conventional cotton. The number one way to be sustainable when using cotton is to use strictly Organic Cotton. (For more info on this check out this post on cotton vs organic cotton)
This is a good segway to explain the difference between slow fashion and sustainable fashion. A brand can be a slow fashion brand and use conventional cotton. However a brand cannot be sustainable whilst using it. To be sustainable you need to using organic cotton only. Look for GOTS or OEKO-Tex certifications.

Sustainability does not only apply to what is used for the clothing, its also about how the clothing is made. What does the company do with its waste? This can be dye-stuff waste or material waste from the cutting room, production lines, shipping materials. If you receive a package from a 'sustainable brand' that is wrapped in 10 tissue papers and has 3 cardboard 'thank you' cards and other promotional materials, they are not being quite sustainable, are they?

Vegan Fashion

Vegan refers to the use, or lack thereof of animals. For a brand to be vegan there needs to be no silk, wool, cashmere, angora (and other animal hairs), leather or fur. A vegan brand does not necessarily need to be sustainable, you may see things like PVC (leather coats), Acrylic, Nylon, Viscose, and other plastic-based fibres. However, not all vegan fashion is plastic. You'll also see cotton, hemp, pineapple leather (PINATEX), apple leather, mushroom leather, linen, tencel, cupro, ramie, rayon, etc. 

The thing with vegan brands is that, depending on your ideals, veganism also includes the fair treatment of people (to me personally it does at least) and a lot of fashion brands may claim to be 'vegan' but rely on slave labor and child labor to produce their clothing. Also making a lot of these materials, like acrylic for example, is terrible for the planet.. so is it really vegan if it is doing harm to our planet? Technically because it does not contain animal skins or bi-products it is vegan. So it's up to you to decide ultimately if that should include production or not.

A good example of a vegan brand that is not sustainable are vegan-tshirt brands. They will have mass made t-shirts coming from god-knows-where, with catchy slogans on them promoting veganims and eco-consciousness but they are made using a cotton-polyester blend, toxic dyes and ink. Brands like this are vegan but not ethical or sustainable. 

As you can see there are big differences between all these categories. If all of them are important for you, then try to look for brands that are Ethical, Sustainable, Slow and Vegan. Otherwise you may fall into some marketing tricks that are profiting off of the publics will to do better whilst lacking the knowledge to know the difference.