3 similar cards

[Rev2000]

What does it mean when I get this it showed me 5 of my recourses and want me to pick 3 similar?

[sorryimlikethis]

It will show you a choice when you're able to decide which resources you want to use to finish a stage in your wonder.

For example if you have 2 coins, a wood, a stone and a brick. It will let you choose which resource you want to use to finish 3 of a kind. Maybe there is a stone in one of the piles next to you so you'd prefer to use that as having 2 stones for your last stage is pointless.