An independent or non-partisan politician is a politician not affiliated with any political party or bureaucratic association. There are numerous reasons why someone may stand for office as an independent.
Some politicians have political views that do not align with the platforms of any political party, and therefore choose not to affiliate with them. Some independent politicians may be associated with a party, perhaps as former members of it, or else have views that align with it, but choose not to stand in its name, or are unable to do so because the party in question has selected another candidate. Others may belong to or support a political party at the national level but believe they should not formally represent it (and thus be subject to its policies) at another level. In some cases, a politician may be a member of an unregistered party, and therefore officially recognised as an independent.
Independents sometimes choose to form a party, alliance, or technical group with other independents, and may formally register that organization. Even where the word "independent" is used, such alliances can have much in common with a political party, especially if there is an organization which needs to approve the "independent" candidates.
Independent politicians are not allowed to run for office in Brazil. The Constitution of 1988, in Article 14, §3rd, item V, says that "Are conditions for eligibility: V - party affiliation." However, the Proposal Amendment to the Constitution (PEC) no. 6/2015, authored by independent senator José Reguffe, would allow the independent candidacy of individuals who have the support of at least 1% of the electors able to vote in the region (city, state or country, depending on the election) in which the candidate is running. Currently, members of the legislature can leave their respective parties after being elected, as in the case of senator Reguffe, who left the Democratic Labour Party (PDT) in 2016.