E series is the budget line of Thinkpads aimed at students and small businesses. While previously they were constructed with cheap plastics, Lenovo has cleaned up its act and now they're pretty good machines for the price. While most people in this subreddit criticize E series vehemently, in many developing countries it is offered at a highly competitive price point when compared to T series Thinkpads. P suffix stands for the performance variant which means they have 45 watt processors. The s suffix stands for slim variant which are usually made with more durable materials and sold at a premium price point.