How do I create "groups of users" and set permissions in SQL Server? I am new to SQL Server, and I need to do something like the following:

Create a group of users that will allow them to only SELECT from Table 1, but be able to SELECT, UPDATE, DELETE and INSERT INTO Tables 2 and 3;
Create another group of users that will allow them to SELECT, UPDATE, DELETE and INSERT INTO all three of the aforementioned tables

All three of the tables are in the same database.
May someone please provide some sample code so that I can accomplish something like that? Thanks!
What you can do in sql server is to create a group of permission.
They are called Database Roles. You can use pre-build roles or create some new.
https://docs.microsoft.com/en-us/sql/relational-databases/security/authentication-access/database-level-roles?view=sql-server-ver15
About the group of users you can't with the sql authentication but if you use the windows authentication you can relay on local user groups (uased as login in sql server) or active directory user groups (add them as login in sql server)
https://docs.microsoft.com/en-us/sql/relational-databases/security/authentication-access/create-a-login?view=sql-server-ver15