It's about the latter: phases or stages of life that we consciously contrast to the usual division into age groups and their attributions.
To avoid misunderstandings: There is never just one stage, one phase of life that a person fills at a certain point in their life. You can be a child of your parents, an experienced worker, (grand)father/mother and widower all at the same time. It would therefore also be better to speak of "roles", even if this term does not correspond to the actual translation of "stage".
We don't want to and can't describe all the roles that life brings with it. But it is important to understand that we live in several stages every day.
The stages that we describe here bring with them major and comprehensive changes in living conditions, especially in old age, and leave most people alone with many questions, especially at the beginning of a stage. Some of them, for example the stage of the person to be cared for, are also a nightmare for many people and are therefore suppressed. The changes that a stage brings with it hit those affected and those around them all the harder.
The stages described here all have a great influence on the living conditions and are therefore also consciously perceived by the person. This identification with a stage is therefore much better suited for marketing and product development than addressing people based on an arbitrary age limit, be it 50plus or 65plus.
Since a stage always determines life in connection with other roles/stages, e.g. the caring grandmother or the retiree who loses her partner, there are often conflicts among the stages. In addition, the accumulation of role-specific changes can make excessive demands on the person concerned.
The challenge of a role is usually greatest during the (first) transition to a new life stage, because the person concerned is literally entering "new territory". This situation illustrates a lack of information about new needs and requirements, often accompanied by uncertainty about what "the best" solution is. Advice and needs-based products and services can help here.
Some stages are repeated in life, e.g. the loss of the partner. This is where experience can mitigate the renewed challenges of a stage.
Especially through the painful experiences of a stage, people often develop the need to share their knowledge and experiences in order to make the transition to a stage with their experiences easier for others. This usually takes place informally among friends and acquaintances.
However, the implicit domain knowledge can also contribute to the development of particularly relevant offers in the context of co-creation or user innovation.