A long weekend is a weekend that is at least three days long (so, a three-day weekend), due to a holiday falling on either the Friday or Monday.
Most countries also feature many four-day weekends, in which two days adjoining the weekend are holidays. (Examples can include Easter Monday / Good Friday, and Christmas Day / Boxing Day.)
Further, in many nations, when a lone holiday occurs on a Tuesday or a Thursday, the gap between that day and the weekend may also be designated as a holiday, or set to be a movable or floating holiday, or indeed work/school may be avoided by consensus unofficially. This is typically referred to by a phrase involving "bridge" in most languages.
A special situation exists in France in some elementary schools, where there is no school on Wednesday: thus, any four-day weekend is essentially a "five-day weekend" for the kids and their teachers. Any four-day bridge, for example: Thursday (Holiday) and Friday (bridge day) for Ascension, is essentially a "five-day weekend" to some teachers.
Four-day bridge weekends are commonplace in non-English speaking countries, but there are only a couple of examples in English-speaking countries:
In the USA, the fourth Thursday of November is Thanksgiving; but the adjacent Friday is made in to a non-working day at some businesses. In Melbourne, Australia, the Melbourne Cup holiday is a Tuesday, but very many people modify their work arrangements to have the Monday off.
In the United Kingdom and some other British Commonwealth countries, and in Ireland, the term is often known as a Bank Holiday weekend, since bank holidays always fall on Mondays.
The term for a four-day weekend in some Spanish-speaking countries is puente ("bridge") or simply "fin de semana largo".
In Spain, the bridge becomes a puente in some years when the anniversary of the Spanish Constitution of 1978 (December 6) and the Blessed Virgin Mary's Immaculate Conception (December 8) and a weekend plus a movable holiday form a block of five days.