Annuals
From the Latin annus, meaning 'year' - and that's how long these plants take to grow from seed, flower, have sex, make more seed and die. Annuals are great for creating instant effects. There are two types:

1 Half-hardy annuals such as cosmos, petunia and salvia die if exposed to the cold, so they can't go into the garden until after the last frost.   Their seeds should be sown indoors in Spring and planted out mid to late May. The plant will keep going until killed by the first autumn frost.

2 Hardy annuals
Hardy-annuals such as corncockle, love-in-a-mist and nasturtium can withstand the cold, so you sow their seeds utdoors in spring: March or April. There's less work involved in raising them than with half-hardy annuals.

Biennials
Latin again - this time 'biennis' means 'two years', so no prizes for guessing that biennials flower not in the year they are sown but the following one. But, because these days we all want instant gratification, biennials are not widely grown. A familiar biennial is foxglove, more unusual is Echium wildpretii.

Perennials
This time the Latin 'perennis' means 'many years'. Sometimes called 'herbaceous perennials', which simply means they 'disappear' in winter. In fact, they die back to a rootstock where next year's shoots are protected and then magically grow back each spring. For example, delphiniums, hostas, lupins, primroses.

1 Perennials survive frost and stay in the ground all year round, for example, peony and lupin.

2 Half-hardy perennials (tender perennials) will not survive frost and must be brought indoors during the winter, for example, pelargonium, fuchsia, and heliotrope. Individual microclimates and good free-draining soil can make an enormous difference to their ability to survive the winter.

AND FINALLY...the Bedding Section  (no not sheets and pillow cases)
Bedding plants are really all plants that, irrespective of their growing habits, are used to make a temporary show. For example: hardy bulbs (hyacinths and tulips), hardy and half-hardy perennials (chrysanthemums), and even tender shrubs (castor oil plant).

Thanks to Alan Titchmarsh for crystal clear gardening info  more at BBC Gardening  Alan has written a very clear set of modules on "How to Be a Gardener".  Have a look and see what you think!