If you worked with SQL before you've probably been using
INSERT to insert rows into a table. A less known feature is the ability to insert multiple rows with one query.
If you want to insert two persons into a table, you can simply call
INSERT INTO twice:
INSERT INTO persons (name, age) VALUES ('Phil', 36); INSERT INTO persons (name, age) VALUES ('Mary', 50);
That works just fine, but there's also a way to do the same with one query:
INSERT INTO persons (name, age) VALUES ('Phil', 36), ('Mary', 50)
The difference is small, but the second query only sends a single command to the server. You will have a hard time to see an impact on performance if you just add two rows, but if you batch process a lot of data you gain a measurable speed difference if you insert multiple rows with one command.