An example of check types on the 757 you have a line a check every 600 hours and a 2a hangar check every 1200 hours. During a line a you get the basic of servicing which could include simple eng apu filter replacements and system replenishments, some simple lubrication of the gears inspection of the cabin and hold and some equip cooling filter replacements.
A hangar a involves much of the same but at a greater level and would include flying control lubrication and deeper inspections, heavier engine servicing ie ignitor plugs, fuel and oil filters and so on.
C checks are usually every year but can run as long as 18 months. The size of the checks depend on the age of the aircaft and customer work requets and typically come as c 2c and 4c with the 4c being roughly evry 4 years and equivallent to a d check.
During the c check the interior soft furnishings are removed the exterior stripped of removal panels and fairings and the cargo holds stripped. A much deeper inspection is carried out and repairs replacements of components undertaken. Routine items such as lubrication and servicing are carried out in conjunction with the defect rectification.
Companies have a planning department that will basically decide when to do what in accordance with the approved maint schedule and when to incorparate sb's comply with ad's carry out cpcp ( corrosion prevention ) and customer mods ( for example new galleys or an IFE fit).
So as you can see there is not really a concrete answer to what is being asked but I hope this helps, and apologies to anyone if any of this is wrong but it is not that easy to explain.