What does concatenate mean?

Answer 1

well, I've not read about sql, but concatenate maybe from other disciplines means the ability to add (combine) strings.
forexample; bringing together 2 different words to come up with a phrase- ---> "high" + "_School" = high_School

thanks (that's according to me)

Answer 2

add two strings to one
concat("solo"+"learn")=sololearn

Answer 3

Roughly similar:

https://www.w3schools.com/sql/func_mysql_concat.asp