Construction: buy the ITM call at a lower strike; buy the ITM put at a higher strike. Both legs have intrinsic value, so the total cost is high (often 50–100% more than an OTM strangle). The trade-off: the position has positive intrinsic value at entry, so the moves required to hit max profit are smaller than for an OTM strangle.
Rare structure; mostly used by sophisticated traders exploiting unusual put-call pricing dislocations. Most retail traders should default to strangles (cheaper, lower probability) or straddles (cleaner risk profile) rather than guts. The structure exists primarily for completeness in the options strategy taxonomy.