III. Actions or states of an unspecified duration
Je faisais la queue parce que j'avais besoin de billets. --- I stood in line because I needed tickets.
Il espérait te voir avant ton départ. --- He was hoping to see you before you left.
IV. Background information in conjunction with the passé composé
J'étais au marché et j'ai acheté des pommes. --- I was at the market and I bought some apples.
Il était à la banque quand il l'a trouvé. -------- He was at the bank when he found it. <--------------