Unit gets +1+1 at start of its turn. Unit loses Mobilize when damaged.This means that as long as the unit with Mobilize hasn’t received any damage, it will grow by +1+1 at the start of every one of your turns. The units with Mobilize are generally priced in such a way that if they are damaged immediately, they are underwhelming for their cost, if they get the bonus once they are generally on par and if they get it two or more times they are starting punch above their weight.
When an Alpine unit is deployed or added it gets +1+1 for each other Alpine unit you control.So the first one you play gets no bonus, the second one gets +1+1, the third one +2+2 and so on. This means that they can quickly snowball a basic unit into something very strong if left unchecked.