This succulent groundcover (formerly filed under Aptenia) is a hybrid of two ice plant species, M. cordifolium and M. haeckelianum, and very frequently confused with the former, which is a similar plant. The most useful differences for resolving them relate to leaf color (brighter green for the hybrid) and texture (smooth for the hybrid), and flower color (red, not pink to purple, for the hybrid). The leaves of the hybrid are also not quite heart-shaped like those of the species (which was named for that feature).

"Red Apple" is fast growing in cultivation, though relatively thirsty and not as drought tolerant as many other creeping ice plants. It will tend to grow rampant given permissive conditions and strangle out other plants (by smothering them above ground and outcompeting them below ground).

There are 4 related plant entries in the database, with some images apparently misfiled among the group at the moment.

One is a species with pink to purple flowers (usually).
Baby Sunrose (Mesembryanthemum cordifolium)

One is an all-green hybrid of cordifolium with red flowers called "Red Apple", which is very common in cultivation.
Baby Sunrose (Mesembryanthemum 'Red Apple')

And one is a very common sport of "Red Apple" with marginal variegated leaves called "Mezoo" (sometimes erroneously filed under Doreanthus or Dorotheanthus). That may be the same as this plant
Baby Sunrose (Mesembryanthemum Mezoo™ Trailing Red)
though I suppose there may be a whole line of Mezoo plants, given the trademark involved.

Our database also includes an entry for variegated M. cordifolium. Most of the plants shown there at the moment would seem to be "Mezoo".
Baby Sunrose (Mesembryanthemum cordifolium 'Variegata')