One thing that separates Swedish from English is that you can often make active verbs in Swedish passive by simply adding an -s to the end of the active form. For example:
att sparka (to kick) → att sparkas (to be kicked)
We can use each of these forms of the word in a sentence to clarify the difference:
Tobias sparkade_ mig. – Tobias kicked me.
Jag sparkades av Tobias. – I was kicked by Tobias.
This method of making active verbs passive can be used on any transitive (object-requiring) verb. Intransitive (object-rejecting) verbs cannot, however, be passivated, but that’s not something you really need to think about since it wouldn’t make sense to. For example, dansa is an intransitive verb:
Kalle dansade över golvet. – Kalle danced across the floor.
*Kalle dansades över golvet. – *Kalle was danced across the floor.
The second example doesn’t make sense. Like in English, you probably won’t be prone to forming passive verbs that don’t make sense, so this is a rule that you probably don’t need to remember.
Another way to make an active verb passive is by applying this formula:
att bli [verb in past participle form]
Jag blev sparkad av Tobias. – I was kicked by Tobias.
As this form is more similar to the English way of saying it than the -s-passive, you may want to stick to it at first, but be able to recognize the -s-passive. Like the -s-passive, though, keep in mind that it does not work for intransitive verbs. Also, there is a slight nuance between the -s-passive and the bli+participle passive, but to be able to recognize it, you should get some practice with native or experienced Swedish speakers.
As a side note, there are verbs that do end in -s and are not passive, such as att hoppas (to hope), att finnas (to exist, to be), and att låtsas (to pretend). These verbs are called deponense verbs and have active (contrary to passive) meanings.