Sony Xperia Tipo has two USB connection mode, MTP and MSC, MTP is media transfer mode which has something to do with DRM protection stuff.
While MSC is mass storage mode, which turn your phone into storage device when connected to PC (it's like USB stick or hard drive).
MTP only works on operating system that has DRM such as microsoft windows, MTP won't work on linux operating system.
And to switch between MTP or MSC is easy, all you have to do is go to the phone "Settings" and then select "Xperia", then select "Connectivity", and finally select "USB Connection Mode".
So basically, with MTP mode you will get access to the internal phone storage which in this case xperia tipo has 2 GB of user available storage, and also you'll get access to your SD card too. And with MSC mode you can only access your SD card but with a lot faster speed than MTP mode.
Media transfer mode (MTP) :
Manage files, update phone software, connect via wi-fi. The most common protocol for communication with windows computers. This mode is enabled by default.
Mass storage mode (MSC) :
Manage files, update phone software. The most common way to connect phones with media devices such as TVs, car kits, and MAC OS/Linux computers lacking MTP support.