Can someone ELI5, what it means to have the typescript compiler built into a V8 snapshot?

This StackOverflow post mentions that the typescript compiler is included in a V8 snapshot. Could someone explain what this means in more clear terms for people using the typescript support? I understand that deno uses the same Javascript interpreter, but how does the typescript support work? Does it essentially transpile it at the start of the application? Does using typescript in deno effect the startup time of the application?

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[deno]

Here is a great take by core contributor Kitson Kelly.