simple past tense and past participle of attempt
"The thief attempted to break into the house but was caught by the security guard."
In plain English: To attempt something means to try doing it even if you might fail.
"The thief attempted to open the back door but failed."
Tried, with the connotation of failure.
"The thief attempted to break into the house but was caught by the police before he could open a single window."
In plain English: Attempted means something was tried but did not succeed.
"The attempted robbery was stopped by the security guard before any money could be taken."