Plugin - pass values from entity to entity

Hello guys.

im new at Crm and Im doing my first steps.

Ive done the sample plugin of sdk (the annotation plugin), but now I wanna do aome experiences.

so… How do I get values from entity X and pass it for entity Y (they have 1:N rellationship) ? For exemple get status of X the change field of Y dependong on that X status.

im not asking for code, just some tips

thanks all