Being an ally is important to the LGBTQ+ community.  Allies can help move things forward, protect members in difficult situations, and offer support in general.

What is an ally?

The following definition is provided in the Fondation Émergence lexicon:

An ally is generally a heterosexual, cisgender person who supports people of different sexual orientations, gender identities, and gender expressions in order to contribute to their well-being or greater acceptance of their realities. However, an ally can also be an LGBTQ2+ person who supports communities other than their own (e.g. a lesbian woman who is an ally of trans people).

You can be an ally without being involved in the community.  By defending someone, by speaking up when you witness stigmatization (intimidation, harassment, discrimination, micro-aggressions, etc.), by informing yourself to better understand the LGBTQ+ reality, you become an ally.
You can be an ally as an LGBTQ+ person yourself.  When you offer support to other members of the community who do not identify as you do, you are an ally. This means getting to know and understand the reality of other members of the LGBTQ+ community that you may never have been exposed to.

Who’s an ally?

Friends and family are often the closest allies of an LGBTQ+ person. They are the ones who are there when things are more difficult.  They are the ones who offer support by listening and validating the person.
They are also colleagues and bosses.  These allies play an important role in providing support but also in encouraging change in the workplace.  They are the ones who help transform work environments, at least for the individual, and sometimes for the workplace as a whole.
They are also professionals and advocates who serve the LGBTQ+ population.  It could be in schools, in health care, in government, or in the justice system.  By showing solidarity as allies, these people can really help the LGBTQ+ population.  This means treating them with respect, creating a positive space for their LGBTQ+ clients, and understanding what their needs are.
Businesses can also be allies by making sure their staff is open and respectful.  There are stickers that can be placed in the window, on the door, or at the cash register to indicate that they are inclusive.  However, it’s important to ensure that staff are aware of the needs of the LGBTQ+ community and that this is reflected in the service offered by all staff members.  It can also be indicated on an e-commerce site by adding a rainbow flag or stating it’s an inclusive space.

​What does it mean to be an ally?

There is no one way to be an ally. It's when you get involved by informing and educating yourself.  It means learning and understanding what the LGBTQ+ community is and what the issues are.  It means accepting that we don't know everything, that it's an ongoing process and that we will make mistakes.  It's about humility and understanding. 
In practical terms, being an LGBTQ+ ally means taking an interest in and getting involved with LGBTQ+ people.  It means speaking out in defence of the LGBTQ+ community.  It's standing up to the discrimination its members encounter.  It's raising awareness to open up the minds of those around you.  It's encouraging a positive climate or creating a safe space.  Sometimes it's as simple as speaking up and speaking out against the degrading comments you hear.  At its core, it's standing in solidarity with the LGBTQ+ community.