tippen
to type
To enter text with your fingers on a keyboard of a computer, typewriter, or smartphone.
Sie kann sehr schnell mit zehn Fingern tippen.
She can type very quickly with all ten fingers.

to type / guess / tap
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to type
To enter text with your fingers on a keyboard of a computer, typewriter, or smartphone.
Sie kann sehr schnell mit zehn Fingern tippen.
She can type very quickly with all ten fingers.

When it comes to computers, smartphones, or keyboards, 'tippen' always means to enter text. Typical objects are 'eine Nachricht' (a message), 'eine E-Mail' (an email), or 'einen Brief' (a letter).
Ich muss meinem Chef schnell eine Antwort tippen.
I need to quickly type a reply to my boss.
To express a guess, 'tippen' is used either with a subordinate clause with 'dass' (that) or with the preposition 'auf' + accusative.
Ich tippe, dass die Gäste bald kommen.
I guess that the guests will come soon.
When 'tippen' means a light touch, it is often used with the preposition 'auf' and an accusative object that indicates the place being touched. The person being touched is in the dative.
Der Lehrer tippte dem Schüler auf die Schulter.
The teacher tapped the student on the shoulder.
In the meaning 'to suspect who or what is responsible', 'tippen' is always used with the fixed preposition 'auf' followed by an accusative object.
Die Ermittler tippen auf einen technischen Defekt als Unfallursache.
The investigators suspect a technical defect as the cause of the accident.
to write
'schreiben' and 'tippen' can both have to do with text. 'schreiben' is more general: you can write by hand, on a computer, or on a phone, and it can also be about the content of a text. 'tippen' more specifically means entering text with your fingers on a keyboard or smartphone. Learners may confuse the words because you can both 'write' and 'type' a message on your phone. However, 'tippen' emphasizes the way the text is entered, not so much the content or the finished text.

Am Abend tippe ich die Adresse schnell ins Handy.
In the evening, I quickly type the address into my phone.
Im Garten schreibt sie eine Postkarte an ihre Freundin.
In the garden, she is writing a postcard to her friend.