who can tell me the best way to memorize all of the Korean vowels?i am confused

why do we use the zero or null consonant in Korean syllable?what is the function of it?

my job i am a biology school teacher , i teach 9th and 10th grades ,i love my job for many reasons :first, i love biology and all the materials that included and i have fun with any thing related to it , second: i like to share any knowledge i have with anyone ,maybe i can help them , third , i think not only my student will learn but also i will learn a lot of things , for example if i know a simple information about one topic i will increase my knowledge by reading books or searching on the internet , so i can give the student more information about it , and being a teacher will help me to have more time discipline , so i wake up early every day and go to school on the perfect time , moreover being a teacher teaches me how to deal with parents specially the annoying one ,finally ,i think school teacher have fun too by talking with the students and listening to their funny story ....so i love this job very much. if there is any mistakes in my topic ,correct it to me please , and wish i can write it in Korean the next time .....

learning korean language i am Thana ,and i grew up in Jordan, Korean language is one of my dreams ,that i will make it true some day ,i want to learn this wonderful language ,so i can meet Korean people then to be a friend with them ,so they can tell me about their fascinated country,culture,traditions ,and their dishes too, actually i don't know any simple thing about this language ,even i don't know the alphabets,but i will learn the Korean alphabet as soon as possible, moreover learning Korean will help me to watch all Korean shows with out struggling with reading subtitles ,so i can have a lot of information by learning this amazing language.