Unbundled access is like going to a toy store where you can buy just one toy without having to buy the whole store.
In the same way, unbundled access is a way for different companies to share important things that they need to do their jobs. For example, let's say there is a big company that makes internet lines (like a toy store with a lot of toys). Smaller internet providers might not have the money to make their own internet lines, but they still need to use them to provide internet to their customers.
So, the big company can "unbundle" their internet lines and let the smaller internet providers use them (like letting someone buy just one toy from the store). This way, the smaller companies don't have to spend a lot of money making their own lines and can still give their customers internet.
Unbundled access can also help create competition between different companies. If only one big company made internet lines, they would be able to charge whatever they want because they have a monopoly (like if a toy store was the only store in town and could charge very high prices for their toys). But if other companies are allowed to use their lines, the big company has to charge a fair price or they will lose business to the smaller companies.
Overall, unbundled access is a way for bigger companies to share their resources with smaller companies, so everyone can do their job and provide services to people who need them.