The past continuous is used to describe actionA general term expressing that somebody or something does somethings which continued over a period of timeThe length of time between two points of time. in the past. This period can be expressed with a time expressionA word or group of words used in a particular situation. E.g.: Good morning, at six, on the sofa, or a clauseA group of related words containing a subject and a verb. with another verbA part of speech that expresses an action or a state. E.g.: John seldom plays tennis. in the past continuous tenseA grammatical category that is marked by verb inflection. To express when an event or action happens in time or when a state exists, we use tenses.. In this case the two actions were happening simultaneously at the same time:

I was looking for you all day yesterday.
He was staying in Rome that summer.
Were you sleeping during the speech?
They were playing cards enjoying themselves while I was cooking in the kitchen.

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A flock of seagulls were following the boat.

Past continuous for actions happening at a particular point in the past
Past continuous Past continuous for developing states