When you select Scratch you will be brought to this page. The image above the Scratch selections will have information about any events occurring in each section.

Friend Scratch (友情)- To perform a friend scratch you will need friend points. To scratch 1 you need 200 friend points. To scratch all 9 (the whole card) you need 1800 friend points. The units you tend to get from this are 1☆-3☆ in rarity including all Evolution Material.

Rare Scratch (レア)- To perform a rare scratch you will need Chips. To scratch 1 you will need 5 Chips. To scratch the whole board (9 squares) you need 45 Chips. You tend to get 3☆-5☆ units from these scratches.

Limited (限定) - Limited Scratch.  These are for limited events, usually collaboration events. Currently, all of the Limited Scratches cost 5 Chips per scratch. Displayed as "Currently In Preparation (準備中)" when no collaboration is underway.