Is it necessary to include "BEGIN" and "END" statements in a SQL script?

Hi.  A programmer came in and helped us generate a lot of SQL code.  I'm a novice SQL user but I can follow along and decipher what steps are being performed so am reviewing to understand the general flow of the application better.  I noticed that in many places the programmer did not use BEGIN and END statements, while in other places, they are being used.  Is this just good syntax or are these statements required to perform some functions while others, not so much?  A couple of the Sprocs with these statements included are simply calling out table updates but same thing is happening in another sproc and the begin/end statement are not used.  thanks