As posted above bedding plants are plants which are typical grown to provide quick easy, usually short lived seasonal colour. Typically they are grouped as autumn (also referred to as winter), spring and summer bedding though when people speak of "bedding plants" they most likely ar referring to summer bedding. These days a very wide range of plants are offered as bedding but traditionally the main group would be. Typically retailers will offer these in packs of 6,9 or 12:
Summer Bedding
Alyssum, Antirrhinum, Begonia, Cineraria, Coleus, Cosmos, Dianthus, Dahlia, Gazania, Impatiens (Busy Lizzie), Lobelia, Marigold, Mimulus, Nemesia, Nicotiana, Petunia, Salvia, Stocks
Autumn/Spring
Bellis, Cineraria, Cyclamen, Myosotis (Forget Me Not), Pansy, Polyanthus, Primrose, Viola, Wallflower
Just to be clear Primrose, Polyanthus, Forget me Not, Narcissus and Hyacinth are all hardy, they are not tender. However most summer bedding plants are tender or at best half-hardy. Begonia semperflorens (the Begonia most commonly grown for bedding) is a half-hardy perennial as are common bedding Geraniums - they are not biennial. A good example of biennial is the foxglove, seed germinates and plants grow in year one, dormant over winter, flower in year two and then die - there are some exceptions but let's not go there.
What ALDI are offering on Thursday are 2 litre pot grown Begonia, Busy Lizzie, Petunia and Marigold. I know where they come from - get in early and they will be good