SQL means Standard language query while T-SQL means Transact- Standard Language Query. SQL is a programming language which major objective is managing relational databases, while T-SQL is an extension of the SQL server. The SQL queries are submitted differently to the database server while the T-SQL writes a program that sends all commands to the server in a simple go.
SQL has many commands, which include SELECT, INSERT, DELETE, CREATE, and DROP, while T-SQL includes special functions like the converted data () and other functions that are not a part of the regular SQL. SQL controls and manipulate data where large amounts of information are stored about clients, product, etc.
while T-SQL has some features which are not found in the SQL these features include procedural programming elements and a local variable to provide more flexible control of how the application flows.