East Africa visa:
This visa covers Kenya, Uganda and Rwanda and costs U$100.
You will need to get this visa if you are doing a trip that starts in Kenya and covers these 3 countries, this goes for most nationalities.
It is valid for 90 days and allows multiple entries.
This visa needs to be applied and paid for online before travelling through:https://evisa.go.ke/evisa.html
If you are coming from Uganda or Rwanda on your tour, you should have already obtained the East African visa from Uganda or Rwanda Immigration respectively, and can enter Kenya with this visa.
Kenya visa:
Most nationalities need a visa for Kenya, this needs to be applied and paid for online before travelling though the following link: https://evisa.go.ke/evisa.html
This visa is valid for 3 months and does allow one re-entry if you have not left East Africa.
This visa is best for those just travelling in Kenya and/or Tanzania. And not visiting Uganda or Rwanda
Citizens from Hong Kong travelling in East Africa need just a Kenya visa as Uganda and Rwanda are visa free.
South Africans and most other African nationals as well as Singaporean nationals are visa free.
Kenyan transit visa:
If you are staying in Kenya for less than 3 days and are leaving through a different border than you entered through (eg of you fly into Nairobi and then travel to Tanzania on tour within three days, or travel from Tanzania straight to the airport) then you can obtain this visa which is U$25.
This visa also needs to be applied and paid for online through this link: https://evisa.go.ke/evisa.html
The East Africa visa/Kenya visa is a full page visa.