What is the difference between the Free and Pro plans?

The difference between the plans is in the features. Both plans have unlimited links, affiliates, and referrals.
​
The standard free plan lets you create referral links with random IDs, which is sufficient for most basic affiliate programs. The links look like this: www.youstore.com/r?id=ie3ejs
​
The $39/mo plan lets you create "custom links". With these links, you can replace the random ID with a text of your choice, so you can have links like this: www.yourstore.com/hello
​
The $39/mo plan also lets you generate unique discount codes for your affiliates, that they can use to generate referrals. This means affiliates can share a discount code with their followers and if that code is used at checkout, the customer will get a discount, and the affiliate will get a commission.