Erasmus Student Network consists of three big levels. The international level, the national level, and the local level.

International Level

The International Level has three big parts, which it is consting of:

The IB consists of 5 elected board members: President, Vice President, Treasurer, Communication Manager, Web Project Administrator.
The mandate always is for one year. At the Annual General Meeting (AGM), the general assembly of ESN, they get elected by all the present local ESN Sections. 
The headquarters of ESN is located in Brussels, Belgium.
Main tasks of the IB are the representation of ESN towards external stakeholders, the coordination of international projects, standing in for the rights and interests of exchange students and the support of all the national sections, which belong to ESN International.

National Level

The national level is being represented by the National Board (NB). In general all of a countries ESN Sections form the national level (for example: there are 17 ESN Sections in Austria, together all 17 Sections form ESN Austria).
The NB is responsible for the coordination of different National Events, (inter)national projects, the cooperation with the National Agencies and also for linking the Local and International Level, which is probably one of the most important tasks. One big national event they're responsible for, is the so-called National Platform (NP), which is usually taking place three times a year. It's a General Assembly, where all sections within one country come together and have discussion about relevant changes and issues concerning every single level of the Network. It's also about getting to know members from other ESN Sections, share experiences and learn new things.

Local Level

All of the local sections in one country together build the Local Level of the Erasmus Student Network. Currently there are almost 500 different local sections all over Europe.
Every local section has - just like it is on the National and International Level - a Local Board, which has different positions.
Here in Salzburg we're having the position of the President, the Vice President, Treasurer and the Secretary. Additionally to these positions, there are other positions as well, who are responsible for the coordination of different tasks.
The aims of local sections are creating activities in the interest of the exchange students, supporting the integration of the exchange students and helping with the reintegration of returning exchange students, as well as having a representative role towards the universities and local partners and finally coordinating the national programmes on a local level.
Often local sections are being supported by their academic authorities (e.g. in Austria the Student Union ÖH, the International Offices, ...) by helping them with advice or financial support, equipment, ... to be able to create an enriching exchange environment for all international students.

Here you can see, which local ESN Sections there are or look for a specific one.