What it means
Loads is a super common British way to say a lot or plenty. You can use it before nouns, like loads of people or loads of time, or on its own when you mean a big amount. It's casual, easygoing, and one of those everyday bits of UK speech that fits almost anywhere.
Usage examples
"There were loads of people at the market, we could barely move."
"Do not rush, we have got loads of time before the train."
"There is loads of cake left, help yourself."
"We have loads of time before the train, no need to rush."
"I've got loads of messages to reply to, I'll do it later."
Where it comes from
It comes straight from load, meaning a quantity carried at once. From there, loads grew into an everyday informal way of saying a great amount. That sense has been around in English for ages, and in modern British speech it's become a really normal, throw-it-in-anywhere way to mean plenty.