by and bysort are really the same command; bysort is just by with the sort option. The varlist1 (varlist2) syntax is of special use to programmers. It verifies that the data are sorted. by varlist1 varlist2 and then performs a by as if only varlist1 were specified.

Can you Bysort two variables in Stata?

Sort order You can use the sort command in Stata to acheive this. Of course you can order your observation based on ordering one variable, but you can go further and sort your data on multiple variables.

What does Egen group do?

egen creates a new variable of the optionally specified storage type equal to the given function based on arguments of that function. The functions are specifically written for egen, as documented below or as written by users.