1) Labour demand is the quantity of hours demanded by firms.
2) wages fall = labour becomes cheap = firms costs fall = produce more goods = more labour required
3) Labour supply is the quantity of working hours supplied by workers
4) wages rise = larger supply of labour
5) Labour slopes upwards
This is because the substitution effect (workers incentivised to work more to earn more income) is greater than the income effect (as wages rise, workers can earn the same income as before by working less, so workers work less to enjoy more leisure)
6) wages too low = less labour supply = more labour demand = excess demand