This is an annoying little annual and sometimes short-lived perennial, which germinates and rapidly forms a dense mat of rooting stems on the surface of the soil, on paths and in poorly growing lawns. It is also ephemeral and can produce a number of generations in a season. Usually it prefers moist acid conditions on stream banks or tracks and in damp meadows. There are four subspecies defined by the pattern of the seed coat.
It is a Purslane related to Claytonia or Miner's Lettuce which is grown as a winter salad crop, so it might have some culinary uses, but it tastes bland and becomes bitter as it matures. A poultice has been cited for use on festering wounds and for rheumatism in a similar manner as Common Chickweed

The bright green, ovate leaves are glabrous and fleshy with a rounded end and no stalk. The smooth, round stems are brittle and can root where they touch the ground. The dense mat the plant forms is usually about 40mm in height.
The tiny white flowers carry both male and female parts with petals which are about 2mm long, appearing from May to October and are pollinated by insects or are self-pollinated. They remain closed in dull weather, arise in pairs from leaf axils and are extended on a stalk about 8 mm long as they develop and mature to the seed capsule in a matter of weeks.
The seed can survive for a number of years in the soil and germinate after cultivation.

Hoe or hand pull, the top-growth is brittle and the roots are tenacious. If there is a large area of growth, it is probably easier to slice it off with a spade. Dispose of uprooted plants, do not add to the compost heap as they may be carrying seed.
Weedkillers to use:-
A residual herbicide to suppress germination.
Paraquat, Diquat, contact action killing top growth, apply before flowering.
Glyphosate kills the whole plant, but it may be capable of shedding viable seed.

See also Bog Stitchwort Common Chickweed, which can look similar when small.