What do the different types of potato mean?

'First early': These are planted between late February and April, for harvesting in May to August. These varieties give you the earliest 'new potatoes' and are best eaten as lifted, not stored.

'Second early': Plant these between March and May, and harvest May to August, a few weeks later than the first earlies. These ones give heavier yields and can be stored short term.

'Main crop': Plant these in April or May for a September/October harvest. These varieties should give the heaviest crops and they can be stored for many months.

'Salad': These are any potato variety that is primarily used for salad, having a waxier flesh.