How to build a custom NER Model?

Named Entity Recognition (NER) is a Natural Language Processing Technique which is used to extract proper entities in a given text content and classify the extracted entites under pre-defined classes. To put in simple words, NER is a technique used to extract entities such as person names, location names, company names, etc from a given text. NER has its own importance when it comes to information retrieval. Naturally after reading a particular text, Humans can recognize some common entities like person name, date and so on. But to do the same with the aid of computers, we have to help the computer learn and do the task for us. To do so, we can avail services of Natural Language Processing (NLP) and Machine Learning (ML).