Current empirical data of internet usage illustrate the overall dissemination of social networks sites (cf. Bolton et al., 2013). This is especially true for younger people and for informal contexts (cf. Livingstone, Brake, 2010). Although social network sites are widely used by university students, there exist significant differences how  (e.g. Hargittai, 2007).
In general, an emphasis on recreational use of social media can be stated - in contrast to usage related to (formal) learning. Even though the potential of social web applications for formal educational contexts is widely discussed, there is only few research on the phenomenon, how social networks go along with university courses and how students use social media in the context of formal learning (e.g. Kolek and Saunders, 2008; Caruso and Salaway, 2008; Grey, Annabell and Kennedy, 2010; Hrastinski and Aghaee, 2012). Social media allows students to establish informal online learning spaces for collaboration and cooperation which exist parallel to university courses and beyond the control of university staff. These closed groups represent specific elements of Personal Learning Environments (PLE) (cf. Attwell, 2007), which are peer-organized and self-regulated. Research of Selwyn (2009) and Madge et al. (2009) analyzing students’ use of facebook indicates a main focus on exchange of social support and coordination of their studies, rather than on engagement in collaborative learning.Therefore it is important to ask whether the use of social network sites blur the boundaries between socializing and studying (cf. Mori, 2008) and especially between informal, recreational use of social media and formal, learning-related use (cf. Jones et al., 2010, Clark et al., 2009). For example, on a survey about the use of tablet PCs in formal and informal contexts, German students stated that it is not possible to differ between private issues and university work by using mobile media and social networks (cf. Bettinger et al., 2013). In addition, there exists empirical research which indicates that there is only few frequent usage of communication and collaboration tools in LMS and CMS used in university courses (unless it is highly controlled and/or related to assessment) (cf. Grey, Annabell and Kennedy, 2010).

Currently, only few research exists on the questions how and to what extend the potential of social media (especially of closed groups of social networks) is perceived and realized by students (e.g. Hrastinski, Aghaee, 2011) in order to support and enhance their learning processes in formal contexts like university.

Therefore the objective of this paper is to analyze the relation of formal educational settings (university courses) and informal settings (closed groups of SNS). The overall research question is: How do university students use closed groups of social networks to organize learning processes connected to university courses?

Besides socio-demographic data, we focus on the following questions:

• How are the learning processes on SNS related to learning processes within the course?
• Who establishes and who joins the closed groups?
• Which different activities take place in the groups? Can those activities be read as extensions or replacements of students' (offline) activities?
• How are the benefits and challenges of closed groups evaluated by its users?
• Do “typical topics” exist? 
• Do “typical patterns of usage” exist?

Theoretical framework:
From a theoretical perspective, closed social network groups are interpreted as specific "communities of practice“ (cf. Lave, 2009; Wenger, 2009), as elements of Personal Learning Environments (PLE) (cf. Attwell, 2007) and as practices of informal learning which are connected to the formal educational context. The processes of using closed groups of SNS are analyzed based on the Relational Quality Criteria Catalogue with regard to learning motivation, learning process, learning barriers and learning evaluation (cf. Meder and Iske, 2009).

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