Many aspects of teacher appointments are arcane. For a start, people are usually offered the job immediately after the interviews and expected to accept straight away. Asking people who are dazed and wrung out by a gruelling process to make an instant decision is unfair and unnecessary.
You should be able to sleep on it, at least.
If you accept, say that you're doing so "subject to a satisfactory contract and salary". Remember that phrase; say it again and again in your head.
This is the time to negotiate salary. Most people start at the bottom of the main scale, M1, and go to M2 after a year, and so on until they reach M6. Governing bodies can start you on more than M1 in recognition of previous, relevant experience, but you'll need to state your case.
The head should be clear about whether the contract is permanent or temporary and about the salary the school is offering you. More than one-third of NQTs are on temporary contracts for no good reason. Clearly, many schools are discriminating against new teachers. One school rarely renews such contracts, preferring to get a fresh lot of cheap labour each year to keep salary budgets down: a continuous supply of cannon-fodder.
Temporary contracts breedinsecurity, inequality and low status, so you'll find it harder to get loans or a mortgage. Apply for permanent posts - unless you have no choice.
Primary jobs might be in short supply so, if you really like the school, go for it even if it is only temporary. Many such posts are made permanent.
Once you have your feet under the table, keep asking if and when the position will be made permanent. If they can't tell you, start looking for other jobs. Do so publicly so that your school knows you're serious about leaving. It's amazing how quickly contracts can become permanent when the head realises you might leave.
If you decide not to accept, reject the offer as quickly as possible. Treat others as you would like to be treated yourself. Bad behaviour has a way of coming back to haunt you.