TI = Technical Infrastructure

If memory serves this was the PA (Product Area) originally responsible for GCP before Cloud became its own PA. But TI was headed by Urs and is responsible for the internal Google infrastructure (Colossus, BigTable, Spanner, etc).

TI is Technical Infrastructure, organization responsible for management/storage/database/analytics/scheduling, etc. software in datacenters. TI and Cloud used to be different branches in the same PA (product area), but TI consumed Cloud Org once cloud became a priority and now it's a single organization (itself a part of PA which also includes G Suite).

Since external-facing cloud projects have very simple and transparent metrics (unlike internal TI projects), Cloud/TI organization mostly concentrates on cloud projects nowadays.