Simple. Compound. Complex. Compound-Complex.
If you hear or read something that you are certain that you do not understand--or you are not certain if you understand or not--seek clarification.
What did you/he/she mean by that?
What did you/he/she mean by _____?
I don't understand your/his/her question.
I don't understand your/his/her statement..
I don't understand your/his/her request.
I didn't catch that. What did you/he/she say?
I don't know what you/he/she mean?
So, yes, by all means if you realize that you didn't understand something speak up, write back!
Take Responsibility for Clear Communication
Responsibility also means confirming your understanding by rephrasing what you think you heard or what you think you read. Don't assume that you understood. Confirm your understanding with rephrasing.
Similarly when you are asking a question, making a statement, or making a request gently quiz your audience to find out what what they understood. This gives you an opportunity to clarify or to try again when you realize that your audience didn't understand the message that you intended to transmit. In this way you are taking responsibility for conveying your message as clearly as you can and your are taking responsibility for making sure that your message was received as intended.
I just want to make sure that my message was clear.
What am I asking you to do?
What did you understand from what I said?
What did you understand from what I wrote?
What do you understand my question to be?
This allows both parties to make sure the the intended message sent was the message received.
Clear Communication is Key
Taking the time to make sure everything is clear to all parties is key to good working relationships at work. Don't leave questions unanswered; ask them. Don't assume that your audience understood you; quiz them. Don't assume you understood: rephrase your understanding giving your audience an opportunity to confirm your understanding or to try again to communicate the intended message.