If the value of dependent attribute/s is same for some value of the determinant attribute/s in all the tuples then it is a functional dependency.
In the first normal form a table should have a key and contain atomic values which means that a column should not be used to save a multi-valued attribute or two different types of attributes.
Normalization in database is a devised process which tries to make the database design less prone to data anomalies which make the database inefficient and redundant. One can easily make a good database design with some experience but normalization helps to achieve a better possible design; decreasing the odds of some hidden anomaly present in the design.
Entity Relation Model (ER Model) is one of the conceptual data models in which database design is represented in a diagram to visualize relationships among the different data components referred as entities. ER model primarily focuses on the types of entities, attributes and the relationships among them as well as other relationships.
Database is a collection of data organized in such a way that a computer can easily retrieve the information. Data refers to facts which are meaningless unless presented in an organized form then it becomes meaningful information. Computer needs highly structured information and that too efficiently accessible and this is what database provides it.