It seems every installed app leaves around a process, often two or more that just sit there using memory and a little bit of CPU. On a desktop computer that isn't so bad because modern operating systems can push unused memory to the disk and make it seem the computer has more memory than it really has. But this doesn't work on phones. There is only a limited amount of memory and when it's out, it really is out.
It took me quite a while and the use of some memory cleaning utility programs to clean up a few megabytes. (There actually is a market for utility apps that kill other apps!)
This means it is not possible to install many applications on an Android phone. Soon the memory will run out and then you need to uninstall something to make room for new apps, even if you had lots of space on your 32 GB microSD memory card.
In my opinion this is quite a remarkable difference to Apple's iOS, which powers iPhones, iPads and iPod Touch devices. When the user presses the home button, the app that was running is stopped. If the app was in the middle of doing something important, the app can ask the operating system to allow it to run for maximum of 10 more minutes. Then the app will be killed. The app is really gone. It will not consume memory, CPU or any other resources.
This makes it possible to install many more apps on an iOS device than an Android device with comparable memory simply because Apple engineers found out the apps that are not used do not have to be running.
And still one Android device vendor claims: "Android has true multitasking, not just task-switching." If this is the cost of multitasking, I'd rather have task-switching.
P.S. If I'm reading a web page on the Android phone and hit the home button, make a couple of calls and then go back to the web browser, why is it the browser shows the page from the top, not where I stopped reading? This must be some form of multitasking I wasn't familiar with...