Install of 8.425 (and I guess 8.430) Question re your instruction to resave types/sections and templates etc

Hi Sergey, can you explain what "You will only need to re-save sections, types and change template and update its settings." means? - We have 10 sections, 40 categories and about 12 Types in our latest site - along with lots of custom templates.. what do we need to do exactly to update to this version properly? And what do we need to do with templates?

thanks!