Søren Rasmussen is Jens Sørensen's father. Opslag is the image number and number is a reference for that opslag. You can find the Danish records at http://www.sa.dk/content/dk/ao-forside
. I am going to walk you through to find the marriage of Jens Sørensen and Else Katrine Poulsen. Go to the above website. Now, where you see Vælg arkivietype her choose kirkebøger (church books). Where it says vælg amt choose Viborg. Where it says vælg herred choose Fjends and where is says vælg sogn choose Højslev. When the next screen comes up click on Højslev 1874-1883. When the next screen comes up (you need to have Java installed on your computer to see the images) click on opslag 79. When that image comes up just look for number 10.
Sørensdatter would mean daughter of Søren and Sørensen would mean son of Søren. It wasn't until the later part of the 19th century that this system of naming was abandoned (the date varies from parish to parish.
I will send more information on your family later today.