Public subnets can route to the internet (via an Internet Gateway). Private subnets have no direct inbound internet access. A NAT gateway lets instances in private subnets initiate outbound connections (e.g., to fetch updates) without being publicly reachable.
Expanding on the short answer — what usually matters in practice:
A tiny example (an explanation template):
// Example: discuss trade-offs for "public-vs-private-subnet:-what’s-the-difference-"
function explain() {
// Start from the core idea:
// Public subnets can route to the internet (via an Internet Gateway). Private subnets have n
}