There are 2 ways you can Insert and Select to insert data from one table to another. For example, if you have a Customer table with 500 rows, and you want to select any one whos age is greater than 45 then you want copy that into a temp table, then you can use anyone of the below query.
If have the temporay table called #CustomerTemp existing with the same structure as Customer, then
INSERT INTO #CustomerTemp
SELECT * FROM Customer WHERE Age > 45
Above query will insert all the rows that satified the condition from Customer table to a temporary table #CustomerTemp
If you have not created the temp table but you want to create it on the fly by the SQL Server then, you ca use below query
SELECT * INTO #CustomerTemp FROM Customer
WHERE Age > 45
This query also going to copy the same set of records into #CustomerTemp temporary table. But when it executes, if there are not tempory table with that name, then it will create one automatically based of the result set.