It does really depend on what the car is and weather it's a main dealer doing it or not and which service internal it is. But ...
Your average car service includes an engine oil change, oil filter, fuel filter, air filter and often cabin air and pollen filter changes. They will usually check your, coolant, power steering fluid and washer fluid and top up if need be and typically check any drive belts are in good order they will also likely check your brakes, pads and disks and your parking brake/hand brake.
I don't think they are likely to renew your power steering fluid at every service, they might though.
An extended service, i.e. one of the bigger ones that comes along every few years would in addition also typically include; spark plugs, coolant, brake fluid, a total power steering fluid replacement, locks, latches and hinges greased and a generally more thorough inspection of the car, such as seals, pipes/hoses, gaskets, suspension parts and exhaust etc. Although if anything is amiss with those you'll be paying extra on top of the service for them. They will also likely hook it up to some diagnostics and interrogate the computer, see if there ar any errors logged etc, a main dealer will do this at least.
On some cars they will also service the transmission, however these days many come with 'sealed' boxes ...so they don't ...which I don't agree with but ...well anyway that's not relevant here.
A basic 'cheap' service by Bob and Co though is little more than engine oil and some filters as you mentioned.
