Four short explainers on the technology behind everyday apps and devices: what an API does, why two-factor authentication matters, what a chip's nanometre number means and why laptops slow down with age.



Part 1What an API is, explained without jargonThe quiet messenger behind every app that shows weather, maps or payments.
Part 2How two-factor authentication keeps accounts safeA password alone is easy to steal. A second step makes a stolen password far less useful.
Part 3What a chip's 'nanometre' number really meansA 3 nm chip doesn't have 3 nm parts. The number has become a name for a generation.
Part 4Why laptops slow down as they get olderIt's rarely the processor wearing out. Storage, heat and heavier software are the usual culprits.