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A carbocation has a positively charged, sp²-hybridized carbon with trigonal-planar geometry and a vacant p-orbital. Its electron deficiency makes it reactive, while neighboring groups and the molecular environment affect its stability. Alkyl groups stabilize carbocations through hyperconjugation and inductive effects; conjugated π-bonds or lone pairs can provide additional resonance stabilization. These effects help explain why allylic and benzylic carbocations can be especially stable, while vinylic and aryl carbocations are poorly stabilized. Stability also matters in alkene and alkyne additions: it can guide Markovnikov regioselectivity and enable rapid hydride or alkyl shifts to a more stable intermediate. Structural constraints, solvent, counter-ions, and neighboring-group participation can further influence carbocation formation and behavior.