Questions & Answers about אלה אופניים יד שנייה.
אלה means these.
It is the normal plural demonstrative in Modern Hebrew, and it works for both masculine and feminine nouns. Here it matches אופניים, which is grammatically plural.
You may also see אלו, which means the same thing, but אלה is more common in everyday Hebrew.
In Hebrew, present-tense sentences like this usually do not use a separate word for is / are.
So Hebrew says:
אלה אופניים יד שנייה
literally something like:
These second-hand bicycles
but it naturally means These are second-hand bicycles.
This is very normal in Hebrew. In the past or future, Hebrew does use forms of to be.