In mechanical solidarity, Durkheim is comparing society to a machine all built the same way.
It is based on the connectedness. Durkheim argues, that mechanical solid societies are held together by the sameness of experiences and values with the people within them. The reason by the people are the same is that there is a low division of labor or specialization within society.
An example of this would be a rural farming community, where everyone in the community is a farmer, farming the same kind of crops, have similar family structures, they might also follow the same religion and attend the same place of worship. If two farmers meet in the field, they will feel more connected to one another because they see themselves as the same kind of person. Mechanical solidarity is a form of social solidarity, which is based on the sameness of societies members.
These are the societies with a low division of labor and a low specialization that makes people feel connected to one another, so there weren’t very much power differentials. emotional reactions enacted within each individual consciousness are thus afforded the most favorable conditions in which to coalesce together