Parallel (competing) reactions: A -> B (k1) and A -> C (k2). Overall rate of A consumption = (k1 + k2)[A]. Ratio of products: [B]/[C] = $\frac{k1}{k2}$. The faster pathway dominates. Consecutive (sequential) reactions: A -> B -> C (k1 and k2). [B] builds up then decreases — shows a maximum at $t_{max}$ = ln$\frac{k1/k2}{(k1 - k2)}$. If k1 >> k2: B accumulates (second step is rate-determining). If k2 >> k1: B is consumed as fast as formed (steady-state approximation applies). These concepts help understand complex reaction mechanisms and are occasionally tested at JEE Advanced level.