Short version is they cannot govern without a coalition partner, but they gain other rights in the parliament, such as filling important positions in the administration. When they reach 1/3 of the votes, so 33% they have a Sperrminorität, which means they can prevent changes in the constitution and also hinder new judges in the constitutional court.
Also 25% in an election would allow installing parliamentary inquiry commissions, which can be a decent way to obstruct the government by busying the bureaucracy and hogging media time.
Short version is they cannot govern without a coalition partner, but they gain other rights in the parliament, such as filling important positions in the administration. When they reach 1/3 of the votes, so 33% they have a Sperrminorität, which means they can prevent changes in the constitution and also hinder new judges in the constitutional court.
Extra context: Sperrminorität translates to a blocking minority, as in you have enough votes to prevent a 2/3 majority vote.
Also 25% in an election would allow installing parliamentary inquiry commissions, which can be a decent way to obstruct the government by busying the bureaucracy and hogging media time.