Texturizer is a product, a mild version of a relaxer
Texlax is a term they use when using a relaxer to texturize the hair.
The correct term to use that I was always taught was texturizing the hair.
And you can texturize the hair using a texturizer or a relaxer or another chemical or some natural products that will lightly straighten the hair.
Some people texturize their hair to release a little curl or a lot of curl but want to keep a curl pattern so they can easily manage the hair.
Some people texturizer 3 times a year, twice a year, once a year and then there are those that will texturize when they get enough new growth which might be every 6-8 weeks.
Some people can texturize just enough to blend with their natural hair where its hard to tell whether or not they have had a chemical process.
Hope this helps