Many students of English have trouble choosing between these two verbs and deciding which is more appropriate. While they are similar in meaning, they are not identical.
notice: to see, hear, or feel something
・He was late to class, but his teacher did not notice. ・You may notice a numb feeling in your toes.
realize 1: to know and understand the importance of something
・Do you realize that the meeting started an hour ago? ・I realize how much she means to you.
realize 2: to suddenly know something that you had not noticed before
・I suddenly realized that the taxi driver was going the wrong way. ・Bill didn’t realize his mistake until the next day.
The definitions of realize include the word “know”, while the definition of notice includes “see, hear or feel”. In other words, realizing is something which involves thinking about a situation. Noticing is more of a physical event in which something comes to our attention through our senses. It is possible to notice something without realizing that it is important.