Ramming was a valid tactic used in ww2.
Light vehicles, guns, even planes on the ground. Its faster and simpler to just drive over them than try to damage each one with HE.
Now tank vs tank ramming was a desperation move. If you find yourself with diabled gun or fighting a superior tank.
The idea is to use strong (and rather pointed) front corner of your hull and hit a weaker spot on enemy tank. Given the huge mass and enough speed it results in damaging the track and wheels of your target, damaging fuel tanks or engine, disabling the turret or even causing ammo to explode. And of course concussion to the crew - being hit by 30 ton steel beast at 30-40 kph is quite a bang.
There is a small chance that your own tank will stay operating, if the driver is skilled enough and doesn't shed the track or damage front wheel.
Often it was T-34 doing the ramming due to its superior mobility.
In game? I'm glad its not implemented. Saves us from every noob trying to drive into you.