小 before a surname is an informal, friendly way to address someone younger: 小王 (Little Wang), 小李 (Little Li).
culture
In Chinese culture, being called 小 (young) is generally a compliment, unlike 老 (old), which can also be affectionate among friends.
Components
pictograph
小xiǎo
small; little
Pictograph of three tiny grains or sand particles - the central hook is the largest grain, flanked by two smaller specks on either side, suggesting smallness and division. Functions as Kangxi radical #42 in its own right and indexes characters about smallness or fragmentation: 少 (few), 尘 (dust), 尖 (pointed), 尚 (still).
Radical
SmallKangxi #42
The 小 radical, originally three small dots representing tiny grains (Shuowen: 物之微也). Indexes characters about smallness, youth, or fragmentation: 少, 尔, 尘, 尖, 尚, 当. The reduced top form ⺌ appears in 学, 觉, 当, where it stacks above another component.