Complex sentence: For Tumblr, an example would be that all the user informations of Tumblr accounts are stored in the data tier, when a user logs in the data tier will get their information and send it to the processing tier which will show it to the presentation tier.
Split into simpler sentences: For Tumblr, an example would be that all the user informations of Tumblr accounts are stored in the data tier. When a user logs in the data tier will get their information and send it to the processing tier which will show it to the presentation tier.