This is for the students and those on welfare, who most people will generally say cannot invite people to Germany. Theoretically, you can still invite someone to Germany BUT the person has to be able to afford their stay here. This is for example for students who are inviting their parents to attend their graduation or just coming to “check-up” on them.
For students, maybe the invitation letter won’t change much but for those on welfare the invitation letter can save the invitee the need to provide hotel reservations when applying for the visa in Kenya. I assume the student doesn’t have a home large enough to accommodate visitors but if you do, then you can always include that bit of info for the embassy.
The invitee will either have to show bank statements in Nairobi to prove they can afford their stay in Germany OR have a fixed/blocked bank account (Sperrkonto) in a German bank where they are allowed to withdraw €150-€300 a day during their stay here. (How to open a Sperrkonto)