Purslane

This is the same family as Moss Rose. Purslane typically has single petaled flowers.

If you're looking for the edible Purslane, look for the name Portulaca oleracea. Although other varieties may be edible, P. oleracea is the nutritional herb you want. It may even be growing in your yard. Please be certain it is correctly identified before adding it to your salad, though!