What is interaction source for an order?

The channels that users use to access a store are called interaction sources. The source could be a search, a referral link in a website, email, etc.
A user can visit your store multiple times through different sources, so sources are divided into the following two types.
First interaction source - the source of the user's first visit to the store within 30 days.
Last Interaction Source - The source of the user's last visit to the store before placing an order.