Does "playing" card mean entering battlefield or from hand to base?

For me I'm thinking specifically for something like Vanguard Captain, where "When you play me, play 2 recruit unit tokens here**"**

I previously assumed "play" means from hand to base exhausted, but does it specifically mean when it enters a battlefield? I feel like the writing on Vanguard Captain implies it's when the card enters a battlefield, but previously when I played with cards like Solari Chief I had assumed it just meant when I played it from my hand to base, was when I thought I could use the effect.

Related; do you use the effect again if you were to ressurect a card from trash with a card like Spectral Matron?