Electric Vehicles (EVs) are becoming the new standard for mobility all over the world. This development is only possible with a good coverage of Charging Stations. To advance the roll out of charging infrastructure, open communication standards play a key role: to enable switching from charging network without necessarily replacing all the Charging Stations, to encourage innovation and cost effectiveness and to allow many and diverse players participate in this new industry. Additionally, the EV charging infrastructure is part of the Smart Grid, a larger and still evolving ecosystem of actors, devices and protocols. In this Smart Grid ecosystem, open communications standards are key enablers for two-way power flows, real time information exchange, demand control and eMobility services. The Open Charge Point Protocol (OCPP) is the industry-supported de facto standard for communication between a Charging Station and a Charging Station Management System (CSMS) and is designed to accommodate any type of charging technique. OCPP is an open standard with no cost or licensing barriers for adoption. The goal of this document is to describe a number of architecture related topics for OCPP 2.0.1. OCPP was originally intended for two way communication between a backoffice, in OCPP the Charging Station Management System (in this document: CSMS) and a Charging Station. The protocol has become more advanced and with every new revision new functionalities and options are added. It has evolved into a protocol that can be used in different architectures for different types of Charging Stations. This document describes, in addition to the original "simple" setup CSMS <> Charging Station, a number of topologies as an additional explanation for using OCPP. Furthermore, the Device Management concept to configure and monitor any type of Charging Station, the OCPP Information Model and the 3-tier model are explained. This document is partially informative and partially normative and is not intended to limit the use of OCPP. However, it does add an explanation what kind of use of OCPP the creators of OCPP had in mind when creating this version of the specification. This document is therefore also intended to support the reader of the protocol specification in Part 2 of OCPP to understand how it can be used.