Fock–Goncharov coordinates describe Hitchin components as the positive part of the character variety. We give an introduction to the underlying notion of positivity for split real Lie groups, as well as a generalized notion of positivity, called \(\Theta \) -positivity, for real semisimple Lie groups introduced by Guichard–Wienhard (European congress of mathematics. Proceedings of the 7th ECM (7ECM) congress, Berlin, Germany, July 18–22, 2016. Zürich: European Mathematical Society (EMS), 2018, pp. 289–310. ISBN: 978-3-03719-676-2. https://doi.org/10.4171/176-1/13 . arXiv: 1802.02833 [math.DG], Generalizing Lusztig’s total positivity. To appear in Inventiones Mathematicae. 2022. arXiv: 2208.10114 [math.DG].) that characterizes higher-rank Teichmüller spaces. The notion emerges from a choice of a certain subset of simple positive roots \(\Theta \) among all the roots of the corresponding Lie algebra \(\mathfrak {g}\) of the group G. Accidentally, the Greek letter \(\Theta \) is also the initial of the word \(\Theta \varepsilon \tau \iota \varkappa \acute {\mathrm {o}}\tau \eta \tau \alpha \) in Greek which translates to “positivity”. A detailed analysis of the \(\Theta \) -positive structure for the groups \(\mathrm {SL}_n(\mathbb {R})\) and \(\mathrm {Sp}_{2n}(\mathbb {R})\) is included.