You are allowed to open 1 new Stocks and Shares ISA each tax year.
If you opened a new one each year, then over your lifetime you could end up with lots of different ISA accounts with many different companies. It is important to understand though that you are only allowed to pay into one of these Stocks and Shares ISAs each Tax year.
So if for example I have 2 Stocks and Shares ISA accounts, I can only pay into 1 of these each tax year.
There are other types of ISAs too, such as Cash ISAs. You are allowed to pay into different types of ISAs within the same tax year, so I am allowed to put £2,000 into my Cash ISA, and £2,000 into my Stocks and Shares ISA for example.