Balayage
What is it? It is a freehand lightening technique.
People often sum up a lot of hairstyles that are lighter toward the ends of the hair as balayage or ombre regardless of the technique used.
Foilage is a thing - sometimes people think its a typo. It is just a way of describing a balayage like technique done in a foil.
This is used generally when you need to highlight the hair but want a softer more natural look than traditional foil placements.
(A lot of clients are trending back to a full head foil technique though and then having the roots toned darker to soften the colour as opposed to placing the highlights lower down the hair. This way as the toner washes off and the hair grows out the highlights were further up and therefore last longer - hope that makes sense)
Ombre / Colour Melt/ Root Strech
These techniques describe a graduation of colour from the roots to the ends. Usually darker at the roots to lighter or brighter on the ends. This technique isn't just for blonde ends many vibrant colours like purple into pink are done with this technique. Sometimes the hair is pre-lightened but generally the ends are already light. A dark colour is applied into the roots area and stretched down or blended into a different tone for the ends.