In addition is typically used to introduce an additional point or idea that supports or expands on what has already been mentioned. It's similar to saying "also" or "moreover." For example:

- I enjoy playing basketball. In addition, I love swimming.

Here, "in addition" introduces another activity that the speaker enjoys, which is swimming.

In addition to, on the other hand, indicates that something is included with or alongside something else. It implies that one thing is added to another. For instance:

- She is responsible for managing the team, in addition to organizing all the events.

In this case, "in addition to" shows that organizing events is an extra responsibility she has, alongside managing the team.

In summary:

- In addition is about adding another related point.

- In addition to specifies that something is included as well as something else.

Both phrases are useful for expanding or clarifying your thoughts, making them valuable tools in communication.