ء = it called hamza
you can use it in the meddle of the word and at the end
examples:
At the end of the word, hamza can be written in conjunction with any of the short vowels, e.g. with a short /a/ (أ), with a short /o/ (ؤ), or with a short /i/ (ئ), e.g. ‘refuge; (ملجأ), ‘refugee’ (لاجئ), ‘slowing down’ (تباطؤ)
At the end of the word, hamza can also occur not in conjunction with any vowel, and in this case it is written on the line (ء), e.g. ‘burden’ (عبء) and ‘friends’(أصدقاء)