Primers are sealers.
Primer is a term in the industry for indicating a coating applied before the final coat.
Although latex paints are porous and breathe, while oil/alkyd paint are sealers, latex primers would have sealing ingredients added to them. (as a rule)
Base coats/primers are generally flat (no shine) for better adhesion of future coats.
There are many terms in the industry that are misunderstood, such as enamel.
There is no product called enamel in paint. It is a condition.
Paint companies call their high line most washable paint, enamel, as they dry to an enamel like condition.
Terms vary from company to company, although would generally be similar in a given country for marketing reasons, as well as government laws.
Most likely the local term for a sealer here would be "sellador", although I have never noticed how they label them here.
If I were Matilda going to buy the paint, I would ask for a "sellador a base de agua", although they frequently call it "acrilica" as latex paints are made with acrylic polymers.