EQ = normal. you can square off in this segment, i.e. intraday is allowed. most of the scripts are traded in this series and thats why you see EQ frequently.
BE= Trade for Trade. scripts in this segment cannot be squared off. sebi shifts scripts from EQ to BE and vise-verse as per its surveillance mechanism.
E1= partly paid up shares are in E1 series. for example Hindalco during its recent Right Issue had taken Rs 24 on application (the right issue was for Rs.94) the rest of the money will be taken on subsequent calls as fixed by the company. these partly paid up shares are traded in E1 series.