In succulent plants leaves and/or stems are rich in water and have a fleshy consistence:

Succulent plants are for example those of the genus Opuntia, or some ornamental species of Euphorbia, whose leaves are strongly reduced or even absent, the photosynthetic activity being carried out by the fleshy stems:

A similar, fleshy habitus is typical also of some species of salty soils, such as those of the genus Salicornia:

In other cases the fleshy consistence is confined to the leaves, such as in the case of the family Crassulaceae, e.g. in Sedum...

...or in Sempervivum and Jovibarba where the leaves are crowded in a basal rosette resembling an artichoke...:

...while in the genus Umbilicus the fleshy leaves have an expanded blade and a long stalk:

Non-succulent plants are those with thin leaves, and stems which are not particularly rich in water.