I do know the answer to this. In the US, the process goes roughly so:

Workers want to form a union. Workers sign authorization cards allowing a specific union to represent them. The union approaches the company and says, we have enough of your workers who want to join, (50% +1) will you voluntarily recognize that your workers have formed a union.

At this point it can go a few ways. The company can demand proof that there are 50%+1 workers authorizing the union to rep them. A neutral 3rd party will inspect the cards and attest this to the National Labor Relations Board office in that state. Like a public notary or professional witness. This protects the anonymity of the workers.

The company can immediately, or following this process recognize the union. They can go to the bargaining table and strike a deal with the workers, or enroll with the union under the area agreement and get the workers signed up.

The company can refuse, like wikimedia did, and demand it go to an election. A date is set and the workers come in to vote by anonymous ballot wether to be represented by the union.

If the company is some real shitheels they'll start dumping $$ into discouraging the workers from voting yes. They hire a union buster and hold captive audience meetings. The union buster tells the workers any kind of lies and bullshit they want, they are a 3rd party and therefore not liable for the bullshit they spout. They say the company will go bankrupt. The company can't afford to have union workers. Unions are corrupt and suck you dry with dues and don't deliver a better life for you and your family. Etc.

Companies frequently violate labor law during this time period. They give raises and benefits to anti-union workers. They fire union supporters (they will owe these workers back wages later). They lie to their workers, threaten the workers, intimidate the workers. Often this corrupts the election process and if the election fails, it can be overturned and repeated because of the illegal practices of the company and union busters. Their goal is to wear out and drive away pro-union workers by dragging the process on indefinately. When you see pickets, this is often what the picket is about. Informing the public that the company is mistreating the workers violating their right to form a union.

Wikimedia are some real shitheels.

INAL and even further away from am American one, but I shall inboke the law of Cunningham . Having the company recognising or just generally being okay with the union formation makes the whole process easier. No hiding your unionisation activities and such. I believe the role of the union-buster is to dissuade the employees from signing up to it, see if there's any dirt on union leaders to have then fired, and to just generally be a royal pain in the arse for everyone.

If I got the story right a bunch of Blizzard developers got fired because they shared company secrets/IP in the same discord server they discussed their unionisation work, so Blizzard's lawyers found an easy way to get rid of them.