If the parliament passes something that you don't want, you can collect 50'000 signatures and challenges the decision. If you managed to collect these signatures, then the law will voted by the whole population in the next votation (we have like 3-4 votations per year).

On the other hand, if you want to propose a law, you can collect 100'000 signatures and create an "initiative". After evaluation of the feasibility of this law, it will be the subject of a nation-wide votation.