What is the geologic time scale and what are some thing scientists use it for (at least two things)?

Question

Here's my answer could you please verify.

the geologic time scale is a record of the geologic events and life forms in Earth’s history. Scientists use it to understand the past and figure out how the earth progressed.

What are unconformities? I don't really understand the definition that I have (a rock or sediment surface separating two layers of different ages)

What is the relative age of rocks?
I'm pretty sure it's just the age of a rock compared to other rocks but i think i need more detail.

Thank you.

Answer 1

Oh and last thing is how does half-life work